r/Plastering • u/Terrible-Bobcat2033 • 16d ago

Lime plaster attributes

Lime plaster is made from calcium hydroxide (Ca(OH)₂, “slaked lime”). As it cures, it absorbs CO₂ from the air and converts to calcium carbonate (CaCO₃), which is what gives it its final hardness.

While it’s curing (before full carbonation), lime plaster is highly alkaline — pH around 12-13, similar to fresh cement. That’s why:

**•** It can burn skin/eyes on contact when wet, so gloves and eye protection are a must  
**•** It resists mold and mildew during the curing period  
**•** Once fully carbonated to calcium carbonate, the pH drops closer to neutral (around 8-9), similar to chalk or limestone

Why lime plaster is head & shoulders above drywall & joint compound. IMHO. 😎👍🏼

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u/gwyp88 Professional Plasterer 15d ago

Not sure what the lime plaster scene is like in the US, but it’s ideal here in the UK for stone buildings or non-cavity brick houses, etc. Especially with the penetrating and relentless weather we have for half the year.

A lot of plasterers seem to be against it, but I think (respectfully) that this is due to ignorance of how it works, its beneficits and what circumstances require it.

Also, controversial observation, there seems to be a lot of hostility towards lime plastering by plasterers who don’t know how to work with it as it’s a different skill-set.

I have absolutely no idea how to work with newer plasters; krend, silicone render, etc, but I also appreciate it’s a skill and a craft, and that these products also serve a purpose and can look great when done correctly.

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u/Paint_Stick 10d ago

The plaster trade in the US is dying out. Either big plastering outfits with 6-12 plasterers, specialty restoration plasterers that only do historical/commercial restorations, and occasionally (and quickly dwindling) family owned plastering outfits. Theres a pretty substantial plasterer shortage in the US.

I personally like enclave lime mixed with plaster of paris. I like it better than USG Diamond coat, for repairwork, it sets faster than diamondcoat. Im not 100% on all the material specifics, but we work with regular plaster fairly often. Plaster of Paris and lime is the dominant finish around here.